Very good points Lyle, I played around with CF systems and found it can be done if given enough rest btw sessions. For example:
Mon: Speed: For example 2x40-50-60
Tue: Int tempo: For example 5x200 rest 3-4mins
Wed: Rest, therapy
Thur: SE: For example 2x3x90
Fri: High end ext or Int tempo: For example 4x300 rest 4-5mins.
Sat/Sun: Rest, therapy
2 hard/1 off/2 hard/2 off